scholarly journals Characteristics of shock tube generated compressible vortex rings at very high shock Mach numbers

2021 ◽  
Vol 33 (9) ◽  
pp. 096105
Author(s):  
Sajag Poudel ◽  
Lakshmana Chandrala ◽  
Debopam Das ◽  
Ashoke De
Keyword(s):  
Shock Tube ◽  
Vortex Rings ◽  
High Shock ◽  
Mach Numbers ◽  
Very High

The Peak Overpressure Field Resulting From Shocks Emerging From Circular Shock Tubes

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
A. J. Newman ◽  
J. C. Mollendorf
Keyword(s):  
Shock Tube ◽  
Horizontal Plane ◽  
Three Dimensional ◽  
Polar Angle ◽  
Field Measurements ◽  
Initial Development ◽  
Theoretical Predictions ◽  
Mach Numbers ◽  
Tube Exit ◽  
Semi Empirical

A simple semi-empirical model for predicting the peak overpressure field that results when a shock emerges from a circular shock tube is presented and validated. By assuming that the shape of the expanding shock remains geometrically similar after an initial development period, an equation that describes the peak overpressure field in the horizontal plane containing the shock tube’s centerline was developed. The accuracy of this equation was evaluated experimentally by collecting peak overpressure field measurements along radials from the shock tube exit at 0 deg, 45 deg, and 90 deg over a range of shock Mach numbers from 1.15 to 1.45. It was found that the equation became more accurate at higher Mach numbers with percent differences between experimental measurements and theoretical predictions ranging from 1.1% to 3.6% over the range of Mach numbers considered. (1) Shocks do propagate in a geometrically similar manner after some initial development length over the range of Mach numbers considered here. (2) The model developed here gives reasonable predictions for the overpressure field from a shock emerging from a circular shock tube. (3) Shocks are expected to be completely symmetric with respect to the shock tube’s centerline, and hence, a three dimensional overpressure field may be predicted by the model developed here. (4) While there is a range of polar angle at which the shock shape may be described as being spherical with respect to the shock tube’s exit, this range does not encompass the entirety of the half space in front of the shock tube, and the model developed here is needed to accurately describe the entire peak overpressure field.

Failure of Brittle and Ductile Hard Disks Due to High Shock Levels

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
Jianfeng Xu ◽  
Izhak Etsion ◽  
Frank E. Talke
Keyword(s):  
Hard Disk Drives ◽  
Bending Moment ◽  
Ductile Material ◽  
Hard Disks ◽  
Element Analysis ◽  
Ductile Materials ◽  
High Shock ◽  
Small Form Factor ◽  
Outer Perimeter ◽  
Very High

The failure due to accidental drop of magnetic recording disks made of brittle or ductile materials is of great interest in the design of small form factor hard disk drives. In this study, fracture of glass disks (brittle material) and plastic deformation of aluminum disks (ductile material) at very high shock levels caused by accidental drop are investigated using finite element analysis. It is found that failure inception for both disk types occurs at the inside perimeter of the disk. For glass disks, cracks are found to propagate toward the outer perimeter of the disk along distinct radial lines associated with the largest bending moment of the disk. The critical shock level at which failure originates increases with an increase in the clamp diameter, a reduction in the disk diameter, and an increase in the thickness of the disk. Some experimental results are presented to validate the numerical model.

scholarly journals The stability of a trailing-line vortex in compressible flow

1994 ◽  
Vol 269 ◽  
pp. 323-351 ◽  
Author(s):  
Jillian A. K. Stott ◽  
Peter W. Duck
Keyword(s):  
Mach Number ◽  
Compressible Flow ◽  
Numerical Results ◽  
Line Vortex ◽  
Mach Numbers ◽  
The Stability ◽  
Vortex Axis ◽  
Very High ◽  
High Wavenumbers

We consider the inviscid stability of the Batchelor (1964) vortex in a compressible flow. The problem is tackled numerically and also asymptotically, in the limit of large (azimuthal and streamwise) wavenumbers, together with large Mach numbers. The nature of the solution passes through different regimes as the Mach number increases, relative to the wavenumbers. At very high wavenumbers and Mach numbers, the mode which is present in the incompressible case ceases to be unstable, whilst a new ‘centre mode’ forms, whose stability characteristics are determined primarily by conditions close to the vortex axis. We find that generally the flow becomes less unstable as the Mach number increases, and that the regime of instability appears generally confined to disturbances in a direction counter to the direction of the rotation of the swirl of the vortex.Throughout the paper comparison is made between our numerical results and results obtained from the various asymptotic theories.

Guderley reflection for higher Mach numbers in a standard shock tube

Shock Waves ◽  
2011 ◽  
Vol 22 (2) ◽  
pp. 141-149 ◽  
Author(s):  
A. Cachucho ◽  
B. W. Skews
Keyword(s):  
Shock Tube ◽  
Guderley Reflection ◽  
Mach Numbers

Review of Problems in Application of Supersonic Combustion

1964 ◽  
Vol 68 (645) ◽  
pp. 575-597 ◽  
Author(s):  
Antonio Ferri
Keyword(s):  
Combustion Process ◽  
Reaction Rates ◽  
Supersonic Combustion ◽  
Experimental Results ◽  
Air Breathing ◽  
Mach Numbers ◽  
High Mach ◽  
Very High

SummaryThe problem of air-breathing engines capable of flying at very high Mach numbers is described briefly. Possible performance of supersonic combustion ramjets is outlined briefly and the supersonic combustion process is described. Two mechanisms of combustion are outlined: one is supersonic combustion controlled by convection process, and the second is controlled by diffusion. The parameters related to the combustion process are discussed in detail. Data and analyses of reaction rates and mixing phenomena are represented; the flame mechanism is discussed, and experimental results are presented.

scholarly journals Development of a high-performance cryogenic shock tube

1974 ◽  
Vol 66 (1) ◽  
pp. 177-187 ◽  
Author(s):  
John C. Cummings
Keyword(s):  
Shock Waves ◽  
Shock Tube ◽  
High Performance ◽  
Reynolds Numbers ◽  
Cryogenic Liquid ◽  
Test Gas ◽  
Driver Gas ◽  
Mach Numbers ◽  
Quantum Mechanical Effects ◽  
Laboratory Tool

A cryogenic shock tube has been developed as a tool for research in fluid mechanics and low-temperature physics. The shock tube was designed to operate with the test section immersed in a cryogenic liquid. A unique diaphragm-changing mechanism makes this shock tube an economical and practical device. There are several advantages in operating a shock tube at cryogenic temperatures. Shock waves of very large Mach number can be produced. The flow field can be accurately calculated using ideal-shock-tube/perfect-gas theory. Boundary-layer effects are decreased, so that long test times are possible.The cases that were studied are test-gas temperatures of 300, 77, 4·2 and 2·3 °K. Helium was used as both test and driver gas. The largest Mach numbers observed range from 2·4 at 300 °K to 32 at 2·3 °K (several runs at 1·46 °K produced Mach 40 shocks). As the temperature of the test gas was decreased, the observed Mach numbers approached those calculated using the ‘shock-tube equation’.As a laboratory tool, the cryogenic shock tube may be applied in many areas and modified for use in even more. Shock waves with large Mach numbers and flows with large Reynolds numbers can be produced with this device. The rapid increase in temperature and pressure across the shock wave is useful for studies of sublimation, evaporation or chemical reactions. Quantum-mechanical effects in cryogenic materials, superconductors or superfluid helium can also be investigated.

An experiment to measure the recombination rate of oxygen

1963 ◽  
Vol 15 (4) ◽  
pp. 497-512 ◽  
Author(s):  
J. Wilson
Keyword(s):  
Shock Tube ◽  
Laboratory Experiment ◽  
Ultraviolet Light ◽  
Rate Constant ◽  
Recombination Rate ◽  
Dissociation Rate ◽  
Constant Area ◽  
Recombination Rate Constant ◽  
Mach Numbers ◽  
The Ideal

The feasibility of an experiment to measure the recombination rate of oxygen is examined using the ideal-dissociating-gas model. The experiment is to be performed in a shock tube, the shock-heated (and dissociated) gas being cooled by passing it through a Prandtl-Meyer expansion, and then allowed to recombine in a constant-area channel. At appropriate densities and shock Mach numbers it is found that recombination takes place in a distance suitable for a laboratory experiment.Using this technique, the recombination rate of oxygen has been measured at 2700 ˚K. To determine the recombination rate, the absorption of ultraviolet light at a wavelength of 2283 å measured 11 cm downstream of the expansion was compared with absorptions calculated for various values of the recombination rate constant.The measured value of the recombination rate constant of oxygen is in agreement with values calculated from dissociation rate measurements.

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